Holley NH Carb

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Model T Ford Forum: Forum 2014: Holley NH Carb
Top of pagePrevious messageNext messageBottom of page Link to this message  By David Stewart on Saturday, May 03, 2014 - 03:35 pm:

I have tried a Grose Jet and needle and seat float valve, but have been unable to stop flooding. Any Suggestions? Thanks.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mark Strange on Saturday, May 03, 2014 - 03:37 pm:

I have seen in another thread that someone used Timesaver abrasive to lap in the needle to the seat.

On more modern carbs, I have given the needle a few taps with a small hammer while it is in the seat to help deform the seat to match the needle tip. Make sure that the needle doesn't get stuck in the seat if you go the tapping route. :-)


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bob Jablonski on Saturday, May 03, 2014 - 03:42 pm:

Check the cast carb body for cracks at the gas inlet


Top of pagePrevious messageNext messageBottom of page Link to this message  By paul griesse--Granville,Ohio on Saturday, May 03, 2014 - 03:57 pm:

pitch the gross jet---use a good needle and seat. Is your "flooding" problem drips/ flow from the carb or do you mean flooding the engine? Set your float lower if the carb is "overflowing'. good luck--Paul


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jack Daron - Brownsburg IN on Saturday, May 03, 2014 - 04:02 pm:

The biggest problem I have with the seat is the POS gasket that is to hard to make a good seal between it and carb body.You really have to tighten down on them.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bob Jablonski on Saturday, May 03, 2014 - 04:03 pm:

Paul:
David has used both types of valves, problem persists.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Steve Jelf, Parkerfield KS on Saturday, May 03, 2014 - 04:21 pm:

Be sure the hole for the valve is clean, with all remains of old gaskets removed. Use a little bit of non-hardening Permatex on the new gasket.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Kenny Edmondson, Indianapolis on Sunday, May 04, 2014 - 08:10 am:

As Jack stated, the problem is typically the hard gasket and poor thread fit of the newer valves (threads loose). The gaskets in the kits never seal and its to the point where I make my own.

I Air Check the needle valve and seats after in install them to check for leakage. You need a rubber tipped air gun. I put a little air tool oil between the seat and carb body. Then I hold the needle valve in the seat with my finger and shoot air to the fuel inlet fitting. See if any bubbles come out of the oil.


Top of pagePrevious messageNext messageBottom of page Link to this message  By James A. Golden on Sunday, May 04, 2014 - 10:51 am:

Make sure the vent hole on top of the carb bowl chamber actually vents to the outside world.

If that hole is plugged, the air bubble will keep the gas level low enough so the needle valve will never shut the gas off.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Stan Howe Helena, Montana on Sunday, May 04, 2014 - 12:37 pm:

I recently got an NH in that had been "rebuilt" and leaked like a sieve. When I bead blasted it and did the rest of the cleanup there were three gaskets in the boss where the needle valve goes. It came off ebay last winter and I don't know who rebuilt it. The rebuild consisted of a needle and seat and black paint. The passages were partially plugged and the throttle shaft had about .020 play.

As far as the gasket, if the area where the seat screws in is clean, that gasket should hold. Often the sealing area at the bottom of the boss is so corroded that nothing but a lead gasket will hold. I use a little stone in the drill press to clean and smooth that area. Also, often the side wall area is rough and needs to be cleaned up as the outside diameter of some (not all) of the new seats is slightly larger than the originals and if the bottom seating area is not exactly perpendicular to the side wall, the seat can be held on one side from screwing in straight. It will not hurt to run that little stone up and down in the hole a few times and clean up those side walls to give it all a little more clearance. Also, make sure there is not a crack somewhere in the body that is letting gas seep in.

Not to argue with Steve, but in my experience with over 1,000 carbs in the last 12 years there is no need for any sealer anywhere in a carburetor if you have the surfaces clean and correctly surfaced.

I agree about the crap bowl gaskets the don't fit anyway. For the small gasket on the seat, I use the red ones available from McMaster Carr. Far better than those tan ones that come with the seat.

Another thing I see is old floats that either were never cleaned or have so much solder on them they won't float.

Just as an aside, "rebuild" means a lot of different things to a lot of people, I guess. There are some carbs on ebay right now that are being advertised as "show quality." The one in the photo has an old drain valve with a rusty and pitted cross arm. Show Quality???? Not in my shop.


Top of pagePrevious messageNext messageBottom of page Link to this message  By R.V. Anderson on Sunday, May 04, 2014 - 08:46 pm:

I believe that the new NH float valve sets now come with the softer red gaskets. As to "loose threads," I know that these seats, along with the needles, were precisely made to the Ford print, and are essentially a re-issue of the original, so I'd be inclined to attribute poor thread fit to corrosion and/or wear in the iron body.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Stan Howe Helena, Montana on Sunday, May 04, 2014 - 10:58 pm:

And: people running taps through the threaded areas that are the wrong size and TPI. The seat is a 1/4 x 32 TPI, not a 28 TPI, which is the common fine thread. Just about every carburetor thread is a special thread.


Top of pagePrevious messageNext messageBottom of page Link to this message  By David Stewart on Monday, May 05, 2014 - 04:55 pm:

Problem solved. Many thanks to all who responded. James A Golden had the answer. Someone had jammed something in the vent hole.
This 1923 T had not been run in at least ten years. A friend asked me to try to get it running again. The engine and body appear to be in very good shape. Now it can be returned to the owner.


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